Are you sure that it is the CSS? That looks like as if some further rendering might be missing – it could be loading script issue too. Check the javascript console whenever the page loads incorrectly, I have a feeling there might be some errors there explaining the problem.
One last thing you may want to check, if the scripts loading method is set to the defaults (see screenshot). Although that has no impact on script execution, but I can imagine some sort of a 3rd party asset causing a conflict with it.